FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE
Specification
(See Section 10; rule 13)
METHOD FOR MANUFACTURING FAN BLADES AND PROPELLERS
GUPTA SANJAY
an Indian National of D-l, Regency Lakshya, 15 Old Palasi, Indore - 452001,Madhya Pradesh, India.
NAME OF THE INVENTOR GUPTA SANJAY
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Field of the Disclosure:
The present disclosure generally relates to methods used for manufacturing fan blades or propellers.
Particularly, the present disclosure relates to methods used for manufacturing large fan blades or propellers.
Definition(s)
Filled resin system used in the specification means resin system having additives filled therein. Background:
Fan is a device used to create flow within a fluid. Fan consists of a rotating arrangement of vanes or blades that act on a fluid, such as air. Fans produce air flow with high volume and low pressure. Fans may be used in various applications such as climate control, vehicle and machinery cooling systems, personal comfort, ventilation, fume extraction, winnowing, removing dust, air fresheners and the like. Fans are of various types such as a propeller fan, a table fan, an exhaust fan and the like.
Propeller fans transmit power by converting rotational motion into thrust. Propeller fans include aerofoil shaped blades. Aerofoil is a typical two dimensional geometrical close loop shape with aerodynamic characteristics. Aerofoil blade is & three dimensional body made from aerofoil using fan designing process. A propeller is a three dimensional body comprising required number of blades made from aerofoil using fan designing process. Further, the aerofoil shape may be quite thick and if made solid, will be very heavy and costly. Further, if the aerofoil shape is made solid, the solid aerofoil shape will produce high centrifugal forces. In practice, pressure difference is produced between the forward and rear surfaces of the aerofoil blade, and fluid, such as air, is accelerated behind the blade. The fan blade or propeller has two surfaces i.e. one that receives air and another that delivers air.
Propeller fans are used in various operations such as industrial wet/ dry cooling towers, air cooled heat exchangers and the like. However, capacity and size of the industrial wet/ dry cooling towers or the air cooled heat exchangers vary based on the industry of use.

Accordingly, propeller fans are designed based on the size of the cooling towers and heat exchangers. Therefore, for high capacity cooling towers and heat exchangers, large sized fan blades and propellers are required. Operation of these large sized axial flow propellers is continuous and is subjected to high mechanical stresses and adverse operational conditions. Accordingly, there is a need for methods for manufacturing large fan blades that can withstand high mechanical stresses and adverse operational conditions.
Conventionally, large sized axial flow propellers are configured from aluminum sheet, aluminum cast alloy, steel sheet, natural wood and synthetic wood. Most of the conventional material used for making blades causes the blades to be heavy. Further, manufacturing of blades using these conventional material require fabrication and support structure. Blades made from natural or synthetic wood and thermo plastics are less reliable due to lower mechanical strength and high deflections. Accordingly, blades made from conventional material are uneconomical, have low speed and low life. Still further, blades made from conventional material are subject to atmospheric and chemical corrosions due to unfavorable environmental conditions to which such blades are exposed to during operation thereof. Furthermore, the conventional materials used for making these large sized axial flow propellers fail to impart necessary strength to these large sized axial flow propellers. The use of blades made of Fiber Reinforced Plastic (FRP) has been suggested in the prior art. The blades made of fiber reinforced plastic material are typically hollow, however, hollow blades made of fiber reinforced plastic material fail to withstand high stresses and adverse operational conditions and are not recommended for high stress applications. In order to enhance the strength of the propeller structure, the blades are required to be made solid with a monolithic body, thereby making the blade strong enough to withstand crippling, distortion and compression. Accordingly, the hollowness of the blades is filled with a light weight solid material. The light weight solid material should have good adhesion characteristics and should fill the hollowness to form a core. The conventional used method for making propeller blades with cores make use of two sets of molds one set of molds is for making the core, while the other set of molds is for making the blade. However, such a method for making the blade involve more number of steps and accordingly significantly increase the manufacturing cost and manufacturing time associated with manufacturing thereof.

Accordingly, there is a need for replacing conventional material with material that is lighter in weight and that can withstand high mechanical stresses and adverse operational conditions. Further, there is a need for large sized axial flow propellers that are resistant to atmospheric conditions and corrosive chemicals. Further, there is a need for manufacturing methods for manufacture of large fan blades and large propellers that are cost effective. Further, there is a need of manufacturing methods for manufacture of large fan blades and large propellers that produce lighter and stronger large fan blades and large propellers.
Methods of manufacturing large sized blades as known in the prior art methods have drawbacks associated therewith including:
• molding and designing of shank parts/areas being difficult and uneconomical;
• mechanically weak parts/areas are produced in the blades;
• parting surfaces are inevitably formed in the blade causing opening of the blade and water seepage inside the blade which increases the rate of failure of the blade;
• poor bonding between outer surface of core and glass reinforcement layers;
• the core and layers of glass reinforcement are not monolithic, and there are always chances of formation of air pockets between the core and the layers of the glass reinforcement, and there are chances of formation of resin dry or rich area which are undesirable.
Accordingly, there is a need for eliminating the drawbacks associated with the methods of manufacturing large sized blades known in the prior art. Further, there is need for manufacturing of fan blades using fiber reinforced plastic material and making the blades by utilizing a method that involves less number of steps, is quick and economical.

Objects:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a simple and reliable method for manufacture of large fan blades and large propellers.
Another object of the present disclosure is to provide a method for manufacture of large fan blades and large propellers using fiber reinforced plastic material that requires less number of steps, is quick and economical.
Still another object of the present disclosure is to provide a method for manufacture of large fan blades / propellers that are adapted to work effectively in intended operational and environmental parameters.
Yet another object pf the present disclosure is to provide a method for manufacture of large fan blades and large propellers that is cost effective.
Yet another object of the present disclosure is to provide a method for manufacture of lighter and stronger large fan blades and large propellers.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
A method for manufacturing an impeller blade for a propeller of a rotary fluid machine is disclosed in accordance with an embodiment. The method includes the steps of providing a mold having an operative top part with a first mold cavity and an operative bottom part with a second mold cavity, wherein the first mold cavity and the second mold cavity define a contour complimentary to the shape of the impeller blade, thereafter preparing the first mold cavity and the second mold cavity by optionally cleaning, polishing and applying a releasing agent to internal surfaces of the first mold cavity and the second mold cavity, applying at least one gel coat mixture to the internal surfaces of the prepared first mold cavity and second mold cavity.

After preparing the first mold cavity and the second mold cavity and applying gel coat mixture there-to preparing a resin mix, 'a green molded blade' is formed by the following steps:
applying a mixture of resin mix and reinforcement material in a predetermined ratio to the internal surfaces of the first mold cavity and the second mold cavity, lining the second mold cavity with at least one layer of reinforcement fiber web over said layer of mixture such that the edges of said reinforcement fiber web extend substantially beyond the edges of said second mold cavity, lining the first mold cavity with at least one layer of reinforcement fiber web over said layer of mixture such that the edges of the reinforcement fiber web extend at least up to the edges of the first mold cavity, folding the reinforcement web of the second mold cavity to configure a reinforcement loop, assembling the mold by placing of the operative top part over the operative bottom part such that the edges of the first mold cavity are operatively aligned with the edges of the second mold cavity, injecting liquid foam into the reinforcement loop. Once, the green molded blade is formed, the green molded blade is allowed to be cured to form a partially polymerized hardened molded blade and the hardened molded blade is removed from the mold after disengaging the operative top part from the operative bottom part.
Further, the method includes the step of trimming extra resin flashes and finishing the flash cut surfaces after allowing some more time for further hardening of the hardened molded blade.
Typically, the releasing agent is poly vinyl acetate.
Generally, the gel coat mixture includes a filled resin system, an accelerator such as cobalt napthanate and a catalyst which typically is at least one organic peroxide typically methyl ethyl ketone peroxide in a predetermined ratio.
Typically, the resin mix includes additives, such as hardeners, catalysts and accelerators added to a polymer synthetic resin.
Specifically, the polymer synthetic resin is selected from the group consisting of polyester, polyurethane, epoxides, and silicon.
Generally, the reinforcement material has a predetermined form and density.

Typically, the reinforcement fiber web is configured by weaving fibers of reinforcement material selected from the group consisting of glass fibers, carbon fibers, Kevlar fibers or a combination thereof.
Generally, the reinforcement loop is a single lap-jointed loop.
Typically, the liquid foam is polyurethane high density foam that includes polyol alcohol and isocynate catalyst mixed in a predetermined ratio, typically 51:63 under predetermined conditions.
Brief Description of the Accompanying Drawings:
Other aspects of the disclosure will become apparent by consideration of the accompanying drawings and their description stated below, which is merely illustrative of a preferred embodiment
Figure 1 illustrates a perspective view of a large fan blade, manufactured in accordance with an embodiment of the present disclosure;
Figure 2 illustrates a perspective view of a hub for assembling a plurality of large fan blades of Figure 1;
Figure 3 illustrates a front view of an assembly of the plurality of large fan blades of Figure 1 with the hub of Figure 2 for the formation of a propeller;
Figure 4 illustrates a perspective view of a propeller, in accordance with an embodiment of the present disclosure;
Figure 5a illustrates a perspective view of an operative bottom part of a mold with a layer of mixture of resin mix and reinforcement material applied thereto and used for manufacturing a large blade using wet core forming method during fan blade molding, in accordance with an embodiment of the present disclosure;
Figure 5b illustrates a perspective view of an operative top part of a mold with a layer of mixture of resin mix and reinforcement material applied thereto and used for manufacturing a large blade using wet core forming method during fan blade molding;

Figure 6a illustrates a perspective view of the operative bottom part of the mold of Figure 5a depicting a plurality of extended layers of reinforcement fiber web disposed over the layer of mixture of resin mix and reinforcement material applied on the operative bottom part;
Figure 6b illustrates a perspective view of the operative top part of the mold of Figure 5b depicting a single layer of non extended reinforcement fiber web disposed over the layer of mixture of resin mix and reinforcement material already applied on the operative top part;
Figure 7a illustrates a perspective view of the operative bottom part of the mold of Figure 6a depicting extended layers of reinforcement fiber web folded to form a reinforcement loop;
Figure 7b illustrates a perspective view of the operative top part of the mold;
Figure 8 illustrates a perspective view of the assembly of the operative top part and the operative bottom part of the mold depicting injecting of foam liquid mix inside the reinforcement loop; and
Figure 9 illustrates a perspective view of the large fan blade manufactured by wet core forming method.
Detailed Description of the Accompanying Drawings:
The method for manufacturing large size fan blades and large size propellers of the present disclosure will now be described in detail with reference to the accompanying drawings. The preferred embodiment does not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein,
The following description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or

adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Conventionally, large sized blades are made of FRP/Composite material and basically comprise two materials. The first material is a reinforcement material including reinforcement fibers like glass, carbon, Kevlar or a combination of these indifferent forms like roving, chopped strand mat, woven roving and cloth of various densities (weight / unit area). The quantity and type of reinforcement material is typically based on blade size and design. The second material broadly includes polymer synthetic resins of various grades like polyester, polyurethane, epoxies, silicon along with or without additives for UV resistance, fire resistance, color pigments and the like. The second material also includes necessary chemicals like hardener, catalyst, accelerator to achieve a desired polymerization. The quantity and type of resin mix is based on the desired reinforcement and method of manufacturing. FRP/Composite material is preferred for making the blades as FRP/Composite material is lighter and strong. Also, FRP/Composite material is a new generation material having high strength and low density. However, the large sized fan blades and large size propellers can be made from any other suitable material.
Generally the blades are made hollow and in order to provide sufficient strength to large hollow fan blades or propellers, blades having a small thickness (few millimeters) may be sufficient. However, hollowness of the blade structure or the propeller is not desirable for an application that requires high strength. Further, the hollow blade or the propeller are subjected to crippling, cracking or opening during application of high or complex load. Accordingly, in order to enhance the strength of the propeller structure, the blades are made solid with a monolithic body, thereby making the blade strong enough to withstand crippling, distortion and compression. In order to make the blade solid, a light weight solid material is needed to fill the hollowness.

The prior art methods for making blades make use of two sets of molds; one set of molds is for making the core, while the other set of molds is for making the blade. More specifically, the method for manufacturing blades in accordance with the prior art uses a main mold for final curing and a core mold for making a core. However, such a method for making the blade involves a relatively larger number of steps and accordingly significantly increases the manufacturing cost and manufacturing time associated with manufacturing thereof.
The method of the present disclosure is used for manufacturing large size fan blades and large size propellers in a relatively fewer number of steps. More specifically, the method of manufacturing the fan blades in accordance with the present disclosure utilizes a single set of mold for making a cored blade from fiber reinforced material, thereby reducing the number of steps involved in the manufacturing of the blades and accordingly significantly decreasing the manufacturing cost and manufacturing time associated with manufacturing thereof. The method for manufacturing fan blades using foam core in accordance with an embodiment of the present disclosure involves wet core forming during fan blade molding. The method of the present disclosure is used for manufacturing blades for large axial fan assembly, wherein a desired number of blades are mounted on a metallic hub. Large axial fan assemblies are used in a variety of applications such as cooling towers, air cooled heat exchangers. The large axial flow propellers are equipped with large sized axial flow fan blades, more particularly, the length of the axial flow fan blade ranges from 1.5 m to 5.5 m and the length of the axial flow propeller ranges from lm to 4.6m. The operation of the axial flow propellers is continuous and is subjected to high mechanical stresses and adverse operational conditions. The method of the present disclosure enables manufacturing of axial fan assembly that exhibits trouble free long life, good aerodynamic and mechanical design and can withstand adverse operational conditions. Also, the fan blades and the propellers are manufactured using materials such as Fiber Reinforced Plastic (FRP), composite materials and the like. Further, the method of the present disclosure may be generally used for manufacturing large size fan blades with a core. The method of manufacturing blades in accordance with an embodiment of the present disclosure utilizes a single mold. The mold has an operative top part with a first mold cavity and an operative bottom part with a second mold cavity, wherein the first mold cavity and the second main mold cavity define a contour complimentary to the shape of the impeller blade. The mold is manufactured using FRP, engineering plastic, aluminium casting/wrought, extruded aluminium, steel, wood, compressed

laminated wood, compressed wood, natural fibers, any other engineering material /metal or combination of these material as per requirement.
Before starting manufacturing of blades in accordance with the below method, the internal surfaces of the mold are prepared by cleaning, polishing, applying releasing agent and the like. A desired premix of gel coat is applied on all molding surfaces. After this the actual molding process is carried out.
The physical/chemical parameters of materials that are used for manufacturing fan blades and propellers are dependent on the type of material, intended use of the fan blades and propellers, and the operational conditions of the intended use. The manufacturing process is typically carried out at room temperature. However, during resin polymerization, because of exothermic reaction, molded part temperature increases. On the basis of atmospheric conditions and suitability, the atmosphere temperature may increase or decrease.
The disclosure relates to a method of manufacturing large fan blades that are used in such applications as cooling towers and air cooled heat exchangers, such blades can range in individual length up to 20 feet and one piece prop up to 15 ft diameter.
Referring to Figures 1 to 4, general assembling procedure of large fan blades is described. Figure 1 illustrates a large fan blade 10 manufactured using the manufacturing method described below. The large fan blade 10 is assembled on a hub 20 (shown in Figure 2) for the formation of a propeller 30 (shown in Figure 3 and Figure 4).
In order to eliminate the drawbacks associated with the prior art methods for manufacturing large sized blade, the present disclosure envisages a method for manufacturing large sized fan blades, the method for manufacturing the fan blade or propeller in accordance with an embodiment suggests formation of a foam core during molding of FRP blades by utilizing a single mold, thereby eliminating the need for two molds used in the prior art for making foam core and the final blade separately and reducing the complexity of the prior art method. The method for manufacturing fan blade using a foam core involves wet core forming in situ during fan blade molding, i.e. the formation of the FRP blade and the foam core formation is performed in a single step in a single mold.

Referring to Figure 5a and Figure 5b, a mold 100 used for making the blade and the foam core, particularly, the mold 100 used for carrying out wet core forming during fan blade molding is illustrated. The mold 100 has an operative top part 104 with a first mold cavity and an operative bottom part 102 with a second mold cavity, wherein the first mold cavity and the second mold cavity define a contour that is complimentary to the shape of the impeller blade. The method for manufacturing fan blade using foam core includes the step of preparing the first mold cavity and the second mold cavity of the mold, wherein the step of preparing the first mold cavity and the second mold cavity of the mold includes cleaning, polishing and applying a releasing agent to internal surfaces of the first core mold cavity and the second core mold cavity, wherein the releasing agent is poly vinyl acetate. Thereafter at least one gel coat mixture is applied to the internal surfaces of the prepared first mold cavity and the second mold cavity, wherein the gel coat mixture includes resin system, accelerator and at least one organic peroxide in a predetermined ratio, wherein the resin system is a polyester resin filled with a filler, particularly an inorganic material. . The accelerator used is cobalt compound particularly cobalt napthanate and in the range of 1 to 3 percent of the mass of the resin and catalyst/hardener such as methyl ethyl ketone peroxide (1 to 3 percent). The quantity of catalysts, accelerators, hardeners is dependent on the external temperature of the environment. The rule being, higher the temperature lesser is the amount of additives required.
The method for manufacturing fan blade using wet foam core further includes preparing a resin mix and forming a green molded blade, wherein the green molded blade is a blade that is formed inside the mold but has not yet been cured. The green molded blade is formed by applying a mixture of the resin mix and reinforcement material in a predetermined ratio to the internal surfaces of the first mold cavity and the second mold cavity, wherein the reinforcement material has a predetermined form and density and the resin mix includes at least one of additives, chemicals such as hardeners, catalysts and accelerators or a combination thereof added to a polymer synthetic resin. The polymer synthetic resin is selected from the group consisting of polyester, polyurethane, epoxies, and silicon. After applying the mixture to the internal surfaces of the first mold cavity and the second mold cavity, the forming of the green molded blade further includes the steps of lining of the first and the second mold cavities with at least one layer of reinforcement fiber web over the layer of the mixture such that edges of the web extend substantially beyond the edges of the second mold cavity and edges of the web extend at least up

to the edges of the first mold cavity, folding the reinforcement web of the second mold cavity to configure a reinforcement loop and injecting liquid foam therein after assembling the mold.
More specifically, Figure 5a and Figure 5b illustrates the operative top part 104 and the operative bottom part 102 configured with the first mold cavity and the second mold cavity respectively, wherein the mixture of the resin mix and reinforcement material in a predetermined ratio is applied to the internal surfaces of the first mold cavity and the second mold cavity. The reinforcement material has a predetermined form and density. Thereafter, the second mold cavity is lined with at least one layer of reinforcement fiber web over the layer of mixture. The lining of the reinforcement fiber web applied over the second mold cavity is such that the edges of the reinforcement fiber web extend substantially beyond the edges of the second mold cavity. The reinforcement fiber web is configured by weaving fibers of the reinforcement material selected from the group consisting of glass fibers, carbon fibers, Kevlar fibers or a combination thereof.
Figure 6a illustrates a lining of reinforcement fiber web layers 106 of predetermined sizes in a pre-determined sequence along with resin mix as per table 2 (provided herein below) over already applied layer of gel coat mixture made by mixing resin system, accelerator and at least one organic peroxide in a predetermined ratio applied over the second mold cavity as illustrated in Figure 5a and is also referred to as extended fiber reinforcement layers 106. A lining of reinforcement fiber web 108 of predetermined sizes in a predetermined sequence along with resin mix as per table 1 (provided herein below) is also applied on the layer of gel coat mixture applied over the first mold cavity, however the lining of the reinforced fiber web 108 applied over the layer of gel coat mixture applied over the first mold cavity is such that the edges of the reinforcement fiber web extend at least up to the edges of the first mold cavity. Figure 6b illustrates the lining of the reinforcement fiber web 108 applied over the layer of gel coat mixture applied over the first mold cavity. The extended fiber reinforcement layers 106 are folded to obtain a single lap-jointed reinforcement loop.
Figure 7a illustrates the single lap-jointed reinforcement loop configured by folding the extended fiber reinforcement layers 106. Figure 7b a perspective view of the top part 104 of the mold 100. After assembling the mold by placing the operative top part 104 over the operative bottom part 102 such that the edges of the first mold cavity are operatively aligned with the edges of the second mold cavity, liquid foam mix is injected into the inner most layers of the

fiber reinforcement loop and is allowed to expand and form a solid foam core formed integral with the blade of desired density. The liquid foam is a high density polyurethane foam comprising a polyol alcohol and an isocynate mixed in a predetermined ratio, typically 51: 63 under predetermined conditions. Figure 8 illustrates perspective view of the assembly of the operative top part 104 and the operative bottom part 102 of the mold 100 depicting injecting of foam liquid mix into the reinforcement loop by using an injecting nozzle 110.
After forming of the green molded blade inside the mold 100, it is hardened by allowing the mass in the mold to cure. The resin mix and foam undergo an exothermic reaction during polymerization and the temperatures attained by the polymerizing mass is typically in the range of 60 to 80 degrees Celsius. As the temperature starts going down, the partially hardened molded blade is removed from the mold. The hardened molded blade, after removing from the mold is allowed to stand for a period of three to four hours to take the polymerization further and obtain a hardened blade which can be tested by striking the hardened blade and obtaining a ringing sound. The hardened blade is subjected to trimming, wherein trimming of extra resin flashes and finishing of the flash cut surfaces is performed after allowing some more time for further hardening of the hardened molded blade. A solid blade 112 having a core and a monolithic body is as illustrated in Figure 9. In the method of this disclosure, the formation of foam core takes place in situ during the molding of the FRP blade by utilizing a single mold, thereby eliminating the need for two molds used in the prior art for making the foam core and for making the final blade separately and reducing the complexity of the prior art method.
Different sizes of blades require different types of glass fiber reinforcement and different quantity of reinforcement are used. The number of layers, weight and volume of the glass fiber reinforcement are decided based on the mechanical design of the blade. The following Table 1 depicts a sequence of the various reinforcement layers to be applied along with resin mix on the first mold cavity of the operative top part 104 of the mold 100, which has been applied with gel coat mix on the molding surface after polishing and applying releasing agent, polyvinylacetate as illustrated in Figure 5b in the method of manufacturing 22 feet diameter blades in accordance with the present disclosure.

Table 1

s.
No. TYPE OF REINFORCEMENT LAYER & SIZE ( W s L ) IN MTR & LOCATION NO OF
LAYERS WEIGHT KG
01 CSM-300 0.6 x 3.012 Just after gel coat layer 01 0.54
02 WR-360 0.5 x 3.012 lstWR full length layer after CSM layer 01 0.54
03 WR-360 0.5 x 0.612 2ndWR layer from shank side 01 0.11
04 CSM-300 0.1 x 3.012 Full length after 2nd layer of WR 01 0.09
04 UD-1135 0.1 x 3.012 After CSM layer 01 0.355
05 UD-1135 0.075 x 3.012 After UD 1135 layer 01 0.266
06 Roving 1200 + UD-1135 As per volume of shank cavity and few extended up to chest area Several numbers 1.10
The overall weight of the reinforcements used over the first mold cavity of the operative top part 104 of the mold as illustrated in Figure 5b is about 3 kg.
The following Table 2 depicts the sequence of the various reinforcement layers to be applied along with resin mix on first mold cavity of the operative bottom part 102 of the mold 100, which has been applied with gel coat mix on the molding surface after polishing and applying releasing agent poly vinyl acetate as illustrated in Figure Sa, in the method of manufacturing of 22 feet diameter blades in accordance with the present embodiment.
Table 2

S.
N. TYPE OF REINFORCEMENT LAYER & SIZE ( W x L ) IN MTR & LOCATION NO OF LAYERS WEIGHT KG
01 CSM-300 0.6 x 3.012 Just after gel coat layer 01 0.54
02 WR-360 1.0 x 3.012 lst&2nd full length WR layers after CSM layer, extended width wise for folding 02 2.17

03
WR-360 1.0 x 2.412 3rdWR layer from shank side, extended width wise for folding 01 0.87
04 WR-360 1.0 x 1.812 4thWR layer from shank side, extended width wise for folding 01 0.65
05 WR-360 1.0 x 1.212 5thWR layer from shank side, extended width wise for folding 01 0.44
06 WR-360 1.0 x 0.612 6thWR extended layer from shank side 01 0.22
08 CSM-300 0.1 x 3.012 full length after sixth layer of WR 01 0.09
09 UD-1135 0.1 x 3.012 After CSM layer 01 0.355
10 UD-1135 0.075 x 3.012 After UD 1135 layer 01 0.266
11 Roving 1200 + UD-1135 As per volume of shank cavity and few extended up to chest area Several numbers 1.40
The overall weight of the reinforcements used over the second mold cavity of the operative bottom part 102 of the mold lOOas illustrated in Figure 5a is about 7 kg.
Further, additional 1 kg of Tex roving is applied along the periphery of the blade lengthwise.
The overall weight of the reinforcements used in the bottom part 102 of the moldlOO as illustrated in Figure 5a and in the top part 104 of the mold as illustrated in Figure 5b is about 11 kg.
The quantity of resin mix required corresponding to a particular quantity of glass reinforcements is determined based on ratio of glass to resin mix as tabulated below:
Table 3

REINFORCEMENT QTY Kg RATIO RESIN MIX Kg
WR -360 5.00 1:1 5.00
CSM-300 1.26 1:2 2.52

UD-1135
1.24 1:1 1.24
ROVING-1200 TAX 3.50 1:1 3.50
TOTAL 11.00 ~ 12.26
Accordingly, the total quantity of resin mix required for manufacturing a 22 feet diameter blade in accordance with present disclosure is about 12.26kg.
A typical resin mix is prepared by adding 1 percent of "3 percent cobalt octate / napthanate liquid" liquid and 1.3 percent of "50 percent solution of Methyl ethyl ketone peroxide (MEKP)". The polyester resin used has the properties as per table 4.
Table 4

S.N. PROPERTIES UNIT VALUES
01 SPECIFIC GRAVITY — 1.13
02 VISCOSITY @25° C CPS 500-700
03 ACID VALUE mg KOH/mg 17 ±3
04 GEL TIME @25° C MINUTES 15±1
05 PEAK EXOTHERM DEGREE
TIME °C SECONDS 183 40
The method for manufacturing blades includes use of liquid chemicals for generating solid high density foam typically polyol alcohols and isocynates under predetermined controlled conditions in a predetermined ratio; the mass of the liquid chemicals for generating foam is calculated based on internal hollow volume with a desired density. For 22 ft blade 2.4 kg, foam chemical mixture

weight is considered to achieve foam density between 68 -70 Kg/M3. The liquid foam is polyurethane high density foam that includes polyol alcohol and isocynate catalyst mixed in a predetermined ratio, typically 51:63 under predetermined conditions. The speed of mixing and injection is typically 200 gm/ sec at 5°C.The machine can be set for a pre-determined mixing ratio, speed and material quantity.
For covering both mold cavity surfaces with two coats gel coat- 1.0 Kg of gel coat mix is considered. The gel coat is mixed with 2% of 3% cobalt octate liquid and 2.0% of 50% solution of MEKP. The polyester gel coat used has the properties as per table 5.
Table 5

S.N. PROPERTIES UNIT VALUES
01 SPECIFIC GRAVITY — 1.2 ±0.2
02 VISCOSITY FC @ 30° C CPS 40 ±5
03 VISCOSITY BROOK FIELD @ 30° C CPS 4000 ± 1000
04 ACID VALUE mg KOH/mg 24 ±3
04 GEL TIME @25°C MINUTES 10±1
The following table 6 depicts properties of the accelerator i.e. cobalt octate liquid that is mixed in the gel coat:
Table 6

S.N. PROPERTIES UNIT VALUES
01 METAL CONTENT AS COBALT % 3 ±0.2

02
VISCOSITY A max Gardner-Hold t@30°C stroke 0.8
03 SPECIFIC GRAVITY - 0.82 ±0.5
04 APPEARNCE LIQUID BLUISH VOILET
05 FLASH POINT °C 39
The following table7 depicts properties of the hardener MEK.P that is mixed in the gel coat: Table 7

S.N. PROPERTIES UNIT VALUES
01 PAROXIDE CONTENT ACID VALUE % 45-50%
02 SPECIFIC GRAVITY @25°C — 1.168
03 VISCOSITY @25°C CPS 16
04 REFRACTIVE INDEX @25°C 1.483
05 ACTIVE OXYGEN % 8.0 Approximate
06 FLASH POINT °c 107 OPEN CUP
07 GEL TIME MINUTES 14-18
08 FORM & COLOUR LIQUID CLEAR & COLOURLESS

The method for manufacturing the blade or propeller in accordance with the disclosure includes the steps of preparing the die mold, applying gel coat over the cavity surfaces of the top part 104 and the cavity surfaces of the bottom part 102 of the mold 100. For preparing the mold, the molding surfaces of both mold parts are cleaned and applied with wax polish. A liquid releasing agent Poly-vinyl-acetate is typically applied over polished tool parts using a spongy foam piece. This poly vinyl acetate film is allowed to dry. The method further involves the steps of preparing the resin mix, applying the mixture of the resin mix and the reinforcement material in a predetermined ratio to the internal surfaces of the first mold cavity and the second mold cavity of the mold 100. The applying of various layers of reinforcement in a predetermined sequence and having predetermined sizes along with resin mix applied as per table l_on the operative top part 104 of mold 100 and on the operative bottom part 102 of the mold 100 is based on table 2. Total quantity of reinforcement and resin mix is summarized in table 3. The lining applied on the operative bottom part 102 of mold 100 with the reinforcement layers 106 extends substantially beyond the edges of the operative bottom part 102 of mold 100 cavity. However, lining of the reinforcement on the operative top part 104 of the mold 100 extends up to the edge of the operative top part 104 of the mold 100. Now, the reinforcement web 106 of the second mold cavity is folded to configure a reinforcement loop, the operative top part 104 is placed over the operative bottom part such that the edges of the first mold cavity are operatively aligned with the edges of the second mold cavity and liquid foam is injected into the reinforcement loop .
Different types of fiber glass reinforcement are used in accordance with the present disclosure; the following tables 8 to 13 depict properties of copped strand mat -450 that is used as a fiber glass reinforcement:
Table 8

S.N. PROPERTY UNIT VALUES
01 TEX Gm/M2 450 ± 7%
02 MOISTURE CONTENT % BY MASS 0.2% MAX
03 LOSS ON IGNITION % BY MASS 4% ± 0.2

04
FLEXTURAL STRENGTH
DRY MPa 205 Min
(Laminate sheet )*WET MPa 155 Min
The following table-9 depicts the properties of copped strand mat -300 that are used as fiber glass reinforcement.
Table 9

S.N. PROPERTY UNIT VALUES
01 TEX Gm/M2 300 ± 7 %
02 MOISTURE CONTENT % BY MASS 0.2% MAX
03 LOSS ON IGNITION % BY MASS 5% ± 0.2
04 FLEXTURAL STRENGTH DRY
(Laminate sheet )*WET MPa MPa 205 Min 155 Min
The following table-10 depicts the properties of woven rovings -360 that are used as fiber glass reinforcement.
Table 10

S.N, PROPERTY UNIT VALUES
01 TEX Gm/M2 360 ± 7 %
02 YARNS WARP
WEFT YARNS/100
MM
YARNS/100 61 ±5
55 ±5

MM
03 BREAKING LOAD WARP WEFT KG KG 300 Min 280 Min
04 MOISTURE CONTENT % BY MASS 0.5% MAX
05 LOSS OF IGNITION % BY MASS 1%±0.2
The following table-11 depicts the properties of roving -1200 Tex that are used as fiber glass reinforcement.
Table 11

S.N. PROPERTY UNIT VALUES
01 TEX Gm/KM 1200 ± 10%
02 MOISTURE CONTENT % BY MASS 0.2% MAX
03 LOSS ON IGNITION % BY MASS 0.5% ± 0.2
04 TENSILE STRENGTH DRY
(Polyester Rod) *WET MPa MPa 600 Min 500 Min
The following table-12 depicts the properties of roving -4800 Tex that are used as fiber glass reinforcement.

Table 12

S.N. PROPERTY UNIT VALUES
01 TEX Gm/KM 4800 ±8 %
02 MOISTURE CONTENT % BY MASS 0.2% MAX
03 LOSS ON IGNITION % BY MASS 0.5 ±0.2
04 TENSILE STRENGTH DRY
(Polyester Rod) *WET MPa
MPa 600 min 500 n
The following table -13 depicts the properties of UD -MATO- 1130 that are used as fiber glass reinfoTcement.

Table
13S.N. PROPERTY UNIT Weight Tex

Gm/M2 Count
01 LAYER AT 0° 850 ± 5 % 2400
02 LAYER AT 90° 42 ± 5% 300
03 LAYER - 225 ±10% 2400
04 TOTAL WEIGHT GM/M2 1130 ±5%
05 MOISTURE CONTENT % BY MASS 0.2% MAX
06 LOSS ON IGNITION % BY MASS <4.5

After gelling occurs, the FRP blade with foam core integral therewith is released from the mold. The step of removing hardened molded blade obtained after curing the green molded blade includes disengaging of parts 102 and 104 of the mold 100 and taking out the FRP blade with core formed within the cavities of parts 102 and 104 of the mold 100. After allowing this blade some time (3 to 4 hours) for further hardening the extra flashes are trimmed and cut surfaces are finished.
After carrying all the above mentioned activities on the blade, the blade is physically examined for any defects. The blade is further made to pass through other test requirements i.e. Cantilever load/ deflection test etc.
Technical Advancements and Economic Significance
The manufacturing systems and methods of the present disclosure are adapted to manufacture large fan blades and large propellers. Also, the manufacturing systems and methods of the present disclosure are adapted to work effectively in intended operational and environmental parameters. Additionally, the manufacturing systems and methods of the present disclosure for manufacture of the large fan blades and large propellers are cost effective. Further, the method for manufacture of large fan blades and large propellers using fiber reinforced plastic material requires less number of steps, is quick and economical.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical

values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

I Claim:
1. A method for manufacturing an impeller blade for a propeller of a rotary fluid machine, said method comprising the following steps:
• providing a mold having an operative top part with a first mold cavity and an operative bottom part with a second mold cavity, said first mold cavity and said second mold cavity defining a contour complimentary to the shape of the impeller blade;
• preparing said first mold cavity and said second mold cavity by optionally cleaning, polishing and applying a releasing agent to internal surfaces of said first mold cavity and said second mold cavity;
• applying at least one gel coat mixture to said internal surfaces of the prepared first mold cavity and second mold cavity;
• preparing a resin mix;
• forming a green molded blade by

> applying a mixture comprising said resin mix and reinforcement material in a predetermined ratio to said internal surfaces of said first mold cavity and said second mold cavity;
> lining said second mold cavity with at least one layer of reinforcement fiber web over said layer of mixture such that the edges of said reinforcement fiber web extend substantially beyond the edges of said second mold cavity;
> lining said first mold cavity with at least one layer of reinforcement fiber web over said layer of mixture such that the edges of said reinforcement fiber web extend at least up to the edges of said first mold cavity;
> folding said reinforcement web of said second mold cavity to configure a reinforcement loop;

> assembling said mold by placing said operative top part over said operative bottom part such that the edges of the first mold cavity are operatively aligned with the edges of the second mold cavity; and
> injecting liquid foam into said reinforcement loop;

• curing said green molded blade to form a hardened molded blade; and
• removing said hardened molded blade from said mold after disengaging said operative top part from said operative bottom part.

2. The method for manufacturing an impeller blade as claimed in Claim 1 further comprising the step of trimming extra resin flashes and finishing the flash cut surfaces after allowing some more time for further hardening of said hardened molded blade.
3. The method for manufacturing an impeller blade as claimed in Claim 1, wherein said releasing agent is poly vinyl acetate.
4. The method for manufacturing an impeller blade as claimed in Claim 1, wherein said gel coat mixture comprises resin system, accelerator and at least one organic peroxide in a predetermined ratio.
5. The method for manufacturing an impeller blade as claimed in Claim 1, wherein said resin mix comprises at least one of additives, chemicals such as hardeners, catalysts and accelerators or a combination thereof added to a polymer synthetic resin.
6. The method for manufacturing an impeller blade as claimed in Claim 1, wherein resin of said resin mix is a polymer synthetic resin selected from the group consisting of polyester, polyurethane, epoxides, and silicon.
7. The method for manufacturing an impeller blade as claimed in Claim 1, wherein said reinforcement material has a predetermined form and density.
8. The method for manufacturing an impeller blade as claimed in Claim 1, wherein said reinforcement fiber web is configured by weaving fibers of said reinforcement material

selected from the group consisting of glass fibers, carbon fibers, Kevlar fibers or a combination thereof.
9. The method for manufacturing an impeller blade as claimed in Claim 1, wherein said reinforcement loop is a single lap-jointed loop.
10. The method for manufacturing an impeller blade as claimed in Claim 1, wherein said liquid foam is polyurethane high density foam comprising polyol alcohol and isocynate catalyst mixed in a predetermined ratio under predetermined conditions.